`Ali bin Abi Talhah reported that Ibn `Abbas said about the Ayah,

﴿إِنَّمَا الْمُؤْمِنُونَ الَّذِينَ إِذَا ذُكِرَ اللَّهُ وَجِلَتْ قُلُوبُهُمْ﴾

(The believers are only those who, when Allah is mentioned, feel a fear in their hearts)

"None of Allah's remembrance enters the hearts of the hypocrites upon performing what He has ordained. They neither believe in any of Allah's Ayat nor trust (in Allah) nor pray if they are alone nor pay the Zakah due on their wealth. Allah stated that they are not believers. He then described the believers by saying,

﴿إِنَّمَا الْمُؤْمِنُونَ الَّذِينَ إِذَا ذُكِرَ اللَّهُ وَجِلَتْ قُلُوبُهُمْ﴾

(The believers are only those who, when Allah is mentioned, feel a fear in their hearts) and they perform what He has ordained,

﴿وَإِذَا تُلِيَتْ عَلَيْهِمْ ءَايَـتُهُ زَادَتْهُمْ إِيمَـناً﴾

(and when His Ayat are recited unto them, they increase their faith) and conviction,

﴿وَعَلَى رَبِّهِمْ يَتَوَكَّلُونَ﴾

(and they put their trust in their Lord), having hope in none except Him. '' Mujahid commented on,

﴿وَجِلَتْ قُلُوبُهُمْ﴾

(their hearts Wajilat), "Their hearts become afraid and fearful.'' Similar was said by As-Suddi and several others. The quality of a true believer is that when Allah is mentioned, he feels a fear in his heart, and thus implements His orders and abstains from His prohibitions. Allah said in a similar Ayah,

﴿وَالَّذِينَ إِذَا فَعَلُواْ فَـحِشَةً أَوْ ظَلَمُواْ أَنْفُسَهُمْ ذَكَرُواْ اللَّهَ فَاسْتَغْفَرُواْ لِذُنُوبِهِمْ وَمَن يَغْفِرُ الذُّنُوبَ إِلاَّ اللَّهُ وَلَمْ يُصِرُّواْ عَلَى مَا فَعَلُواْ وَهُمْ يَعْلَمُونَ ﴾

(And those who, when they have committed Fahishah (immoral sin) or wronged themselves with evil, remember Allah and ask forgiveness for their sins; -- and none can forgive sins but Allah -- and do not persist in what (wrong) they have done, while they know) ﴿3:135﴾, and,

﴿وَأَمَّا مَنْ خَافَ مَقَامَ رَبِّهِ وَنَهَى النَّفْسَ عَنِ الْهَوَى - فَإِنَّ الْجَنَّةَ هِىَ الْمَأْوَى ﴾

(But as for him who feared standing before his Lord, and restrained himself from vain desires. Verily, Paradise will be his abode.) ﴿79:40-41﴾

Sufyan Ath-Thawri narrated that As-Suddi commented,

﴿إِنَّمَا الْمُؤْمِنُونَ الَّذِينَ إِذَا ذُكِرَ اللَّهُ وَجِلَتْ قُلُوبُهُمْ﴾